Non-disjunction

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The term non-disjunction ( English : disjunction = separation), also known as nondisjunction and by the synonym false segregation , is understood in genetics to mean the failure of two homologous chromosomes to diverge in meiosis I or the failure to separate sister chromatids due to a disruption of the metaphase during mitosis or meiosis II.

The resulting daughter cells either have one chromosome too many ( trisomy ) or one chromosome too few ( monosomy ). Non-disjunction is the most common cause of such aneuploidies .

So-called free trisomies arise due to meiotic non-disjunction, mosaic trisomies arise from mitotic non-disjunction.

swell